A group of inorganic (mineral) compounds are known to effectively bind heavy metals such as lead, cadmium, iron, zinc, and copper. The mechanism by which the minerals bind heavy metals is termed “Phosphate Induced Metal Stabilization” (PIMS) and is widely utilized for the environmental remediation of heavy metals from contaminated soils and water. In environmental remediation applications, bulk quantities of minerals possessing PIMS affinity for toxic metals are mixed with contaminated soil or contained within a housing whereby contaminated water may perfuse through the bulk PIMS mineral cake to reduce heavy metal contamination.
A common failure mode within the lead-acid (or lead-calcium) battery industry is the phenomenon of “hydration shorts”. This type of short circuit is typically formed in batteries when they are allowed to stay at very low acid concentrations (low charge) for an extended period of time. In a charged state, the acid density is high (for example, 1.28 g/cm3) and the solubility of lead sulfate is low. At low charge, the acid density decreases and the solubility of lead sulfate increases. At low charge, lead sulfate (PbSO4), from the electrode plates, enters into the electrolyte solution (sulfuric acid H2SO4). Upon recharging, lead sulfate is precipitated and can form a layer on the bottom of many of the separator pores (the separator pores are large compared to the ionic radii of lead and sulfate). Upon additional recharging of the battery and contact with the negative electrode of the battery, the precipitated lead sulfate can be reduced to lead and thousands of microshorts between the electrodes can be generated (hydration shorts and battery failure).
Typically, this “hydration shorts” phenomenon occurs when a battery encounters a slow discharge as in the case of storage over extended periods without maintenance of charge. The conventional approach to the prevention of hydration shorts consists of addition of sodium sulfate (Na2SO4) to the electrolyte solution during battery manufacture. This approach requires an additional manufacturing step, the addition of sodium sulfate to the electrolyte, and adds complexity to the battery processing. Sodium sulfate addition acts to “hinder” hydration shorts via the Common Ion Effect but does not address the root cause (soluble lead generation).
As such, there exists a need for new or improved battery separators and the like for particular battery applications, particular uses, and/or for addressing, reducing or eliminating the phenomenon of “hydration shorts” in lead acid batteries.